Environmental encasement systems for covering in-place asbestos and lead paint for asbestos abatement and lead paint abatement offer an effective economical means to solve an environmental problem of enormous proportions today. The removal of asbestos from existing installations has not proved satisfactory because of excessive high costs, the requirement to vacate the premises, and the placing of airborne particles that are carcinogenic and otherwise may present a substantial health hazard. Removing millions of tons of asbestos from public and commercial buildings, industrial plants and residential dwellings is an expensive, complicated and, to an extent, hazardous solution. Another problem is the limited number and size of toxic waste sites in the country for disposing of the asbestos.
In the "Green Book" entitled Managing Asbestos In Place, published July, 1990, by the Environmental Protection Agency, the authors discuss response actions for asbestos abatement. Such response actions include encapsulation (covering the asbestos containing materials (ACM) with a sealant to prevent fiber release), enclosure (placing an airtight barrier around the ACM), encasement (covering the ACM with a hard-setting sealing material), and repair or removal of the ACM. In general, encapsulation, enclosure, encasement, and repair are intended to help to prevent the release of asbestos fibers, and the authors recommend assessing as viable alternatives to removal, the processes of encapsulation, encasement, enclosure or repair.
The removal of lead paint also causes hazardous conditions, especially when the lead paint is scraped or sanded, whether inside or outside a building. There is no satisfactory solution currently known for removing lead paint. Fine dust is formed when lead paint is scraped and sanded, and that dust tends to contaminate the air and is especially harmful to children and to elderly people. The covering of lead paint with a hard shell to encase the lead paint offers a viable solution to lead paint abatement.
A commercial material previously used as a fire protective thermal barrier for foam plastics is sold under the U.S. registered trademark Staytex.RTM.. Such material and methods of using such material are disclosed in U.S. Pat. No. 4,122,203, the entire disclosure of which is hereby incorporated by reference. Such material is well accepted as meeting building codes, fire codes, etc. For example, the New York City MEA 52-87-M report indicates acceptability for interior finish usage with Class A flame spread rating and smoke developed rating per US Testing No. 94130 (Feb. 6, 1987). Also, the Toxicity Laboratory of the University of Pittsburgh report dated Jan. 15, 1987 provides a similar indication for the Staytex material when installed over noncombustible substrates. Exposure to fire does not produce products of decomposition or combustion that are more toxic than those given off by wood or paper when decomposing or burning under comparable conditions.
As is disclosed in such patent, a thermal barrier that provides fire resistance is comprised of a continuous phase of a flowable or sprayable synthetic resinous material in which is substantially uniformly dispersed an inorganic salt of a Group II A element of the Periodic Table selected from the group consisting of magnesium, wherein the salt has an excess of 35% by weight of chemically bound water of crystallization, a major portion, and preferably essentially all, of which is driven off when the salt is heated to a temperature from about 200.degree. F. but below about 600.degree. F. The preferred salt disclosed in such patent is magnesium sulfate heptahydrate (MgSO.sub.4.7H.sub.2 O), economically available as epsom salts. Such material contains a high level of water of crystallization, most of which is given up at about 392.degree. F., and the crystals smaller than about 20 U.S. Standard mesh (840 microns) provide the multiple functions of resin extender, fire resistance provider, and flame retardant in the thermal-barrier formed thereof. Many of the features of the Staytex material described in such patent inure to the instant invention.
One drawback to the original Staytex material disclosed in the above patent is the relatively large size of the particles of the salt used. As is described in the examples in that patent, to pump the resin containing the salt crystal particles, e.g., for spraying, the particle size of the crystals was such that all of the crystals had to go through a 20 U.S. Standard mesh screen. The preferred size range is described as from about 20 mesh (0.84 millimeters) to about 200 mesh (74 microns); and as is especially described in that patent, it was essential that the crystals be in a size range smaller than about 10 mesh and larger than those which would go through a 325 mesh screen.
A disadvantage to using relatively large size particles is the inability to spray the resin and salt material by an airless spray system and the difficulties attendant an air spray process. Therefore, often it was the case that the material had to be applied by use of a trowel onto a surface. Such process is messy and usually requires the material to be applied in a special plant or factory, not on a job site in situ. This limitation is contrary to the requirements for on-site application for encasing asbestos and lead paint.
Also, to avoid running, especially when the coating material is applied to a vertical surface, it often is necessary to use a thixotropic agent, such as Cabosil. A drawback to using a thixotropic agent, though, is that it raises the viscosity of the material causing difficulty, and sometimes impossibility, of pumping the material.
When the material was sprayed onto a substrate, air spray equipment was required. A substantial styrene odor would occur during the curing of the material. The air involved in the spray process would tend to distribute the odor over a wide area, and the odor would tend to permeate not only the local job site but also elsewhere in the building in which the material is being applied. The styrene odor sometimes tends to cause nausea, dizziness, and/or other unpleasant manifestations. It has been found that screening the work area by plastic walls, such as using polyethylene sheeting, has been unsatisfactory to date to contain such odors. Also, negative pressure has been unsatisfactory to date to prevent penetrating styrene odors from permeating the external environment, even though negative pressure has been used to prevent release of asbestos particles, for example. Ordinary charcoal and other types of filters also have not been effective to date to eliminate the styrene odor.
Another disadvantage with the air spray process of applying Staytex material is the relative lack of accurate control of the spray stream, which tends to cause unintended areas to be sprayed, thus requiring cleanup and also sometimes resulting in non-uniform coatings. Further, air spray equipment uses air pressure to bring the catalyst into the resin; a drop in air pressure causes a lesser amount of catalyst, possibly resulting in an incorrect amount, e.g., too little, of catalyst being supplied to the resin and, thus, inadequate or incomplete curing.
Still a further disadvantage with air spraying processes is the need to bring all of the equipment, including the supply of Staytex coating material and catalyst, into relatively close proximity to the material being spray coated. This requires substantial labor both to move the equipment to the location, to remove the equipment, and to cleanup the mess often associated with relatively heavy equipment and industrial processes.
Another problem encountered in air spray processes of applying the Staytex material has been the curing of the material in flow-lines. Typically the resin with the salt and a promoter are placed in one tank or container and the catalyst in another; the catalyst is mixed with the primary material, which is sprayed. Once the catalyst starts working with the promoter, curing begins, and it is possible that the material can cure in the flow lines if the system is shut down for too long a period. This requires substantial cleaning of the spray equipment.
Another problem with air spraying the Staytex material relates to the fact that in high humidity areas or where there is water splash on the cured material, granules of the epsom salt exposed at the surface to such moisture may expand, e.g., as in effervescence, and the water molecules may release tending to degrade the surface of the material and also possibly to degrade the fire retarding nature of the material. In the past it sometimes was necessary to apply an additional gel-coat of pure polyester resin, for example, to provide a resin rich surface to assure full enclosing of the salt.